This invention relates to an ignition device for internal combustion engines, and more particularly to an ignition device for igniting the fuel-air mixture by means of the light-beam.
The fuel-air mixture has been conventionally ignited by means of sparking devices, such as a spark plug which is mounted on the wall of an internal combustion engine to produce spark discharge through making use of high-voltage. This type of sparking device has a drawback in that owing to adhesion of carbon to the surface of an insulator and consumption of electrodes in use discharge energy is progressively reduced or electric discharge is difficult to be effected or ignition of the fuel-air mixture.
There has been a problem in connection with the durability of a spark plug which is selectively disposed to extend centrally of the combustion chamber so that electric discharge is produced at a location suitable for ignition in terms of air-fuel ratio in the combustion chamber and flow of the fuel-air mixture.
Ignition devices have been proposed which use a high energy light such as laser beam for igniting the fuel-air mixture. With this type of ignition device, light energy is directly irradiated on the fuel-air mixture. Since the light absorption index of the gases, namely the fuel-air mixture is small, however, it is difficult in this type of ignition device to ignite the fuel-air mixture in a short period of time corresponding to the rotating speed of the engine due to temperature rise attained by the absorption of light energy. Accordingly, ignition of the fuel-air mixture is conventionally attained by dielectric breakdown thereof (plasma state of the mixture) which is caused in the field of high light energy of the order of scores of megawatt. Therefore, it is necessary to provide a light generating device, such as a giant pulsed laser of a large output, which is large in consumption of electric power and is inefficient and large-sized in construction. Thus, this type of ignition device is not practical.